The invention relates to a vibration-decoupling flange connection in the exhaust gas pipeline of motor vehicles said connection including flanges pretensioned by means of a tensioning device with springy means so as to swivel and/or seal on a position, corresponding to a precalculated position of the pipe members to be connected, the tensioning device being mounted when the exhaust gas pipe is closed and forming a clamp, whose clamp legs overlap under pretension the opposite flange sides with their clamp curves, extending over a circumferential angle of more than 180 degrees, and the clamp curves exhibiting supports, spaced in the circumferential direction.
Vibration-decoupling flange connections are known from everyday practice and are provided in particular between the parts of the exhaust gas pipeline that are linked together with articulation so as to seal. Such flange connections are subjected to some extent to significant forces, since the exhaust gas pipe is coupled with the engine of the vehicle and forms a xe2x80x9cleverxe2x80x9d, which projects beyond the engine and is braced, like the engine, so as to move elastically relative to the frame or the chassis of the vehicle and thus contributes to the stabilization of the engine""s position inside the vehicle. The engine must be stabilized with respect to the internal motoric forces and torques, driving torques and forces of gravity. This situation necessitates, on the one hand, a correspondingly stable design of the flange connection and, on the other hand, a design that compensates up to a certain degree for the angle errors and assembly tolerances and that can reduce both the effects of the vibrations of the exhaust gas system and the effects of the exhaust gas system-initiated vibrations and the Ferraria effect. To achieve in this respect a specific decoupling in the flange connection, said flange connection is braced by springy means.
To this end, the DE 44 44 550 A1 (corresponding U.S. Pat. No. 5,873,609) discloses the use of disk spring-like tensioning elements, which envelop the flanges over their periphery and, therefore, cannot be used in the closed exhaust gas pipeline. These tensioning elements are connected in turn to a tensioning device with suitable pretensioning. In so doing, the connection is produced by means of cover plates, which extend in the direction of the exhaust gas pipeline and are one piece with one of the tensioning elements and can be hooked relative to the other tensioning elements, so that the degree of elastic flexibility depends primarily on the spring hardness of the disk spring-like, annularly closed tensioning elements. Such tensioning devices are, to be sure, satisfactory in their function, but necessitate a relatively high demand for expensive spring steel and cannot be used at all in the closed exhaust gas pipeline, so that, for example, damage or failure of the tensioning elements incurs high repair costs. In addition, the totally enveloping construction also necessitates a relatively large space requirement, so that, despite the functionally quite satisfactory result of such tensioning devices there is a demand for tensioning devices that can be used in turn in the closed exhaust gas pipeline.
Also not to be used in the closed exhaust gas pipeline are multipart pipe connections, according to the DE 196 46 125 A1, where there is a centering ring, which acts between the pipe ends to be connected. Said centering ring lies in an enveloping jacket casing tube, which is spaced radially from the pipe ends to be connected and rests against the sets of sealing rings, which can be inserted axially into the annular slit to the jacket casing tube and spreads apart radially under tension. Axial bracing is produced by tensioning rings, which can be inserted into the jacket casing tube from both face sides and locked relative to the jacket casing tube.
Tensioning devices for the closed exhaust gas pipeline, known from the DE 197 28 973 A1, are designed as one piece, U-shaped tensioning clamps, whose curved clamp legs are connected together with a web in their crown area and pass over freely in the shape of a fork into two arms on the opposite side. Since the clamp curves are slid on from the side, these clamp curves of the clamp legs surround the exhaust gas pipeline on both sides. In so doing, the clamp legs rest against one of the opposite flange sides. The flanges to be secured in position are stressed by means of the respective arms of the clamp legs in tensioning areas, which are moved in the longitudinal direction of the arms. In the respective tensioning area, the arms exhibit as a support a recess or the like, by means of which a passage, which is also necessary for the spring effect, is achieved between the respective flange and the arm, braced against said flange.
In another vibration-decoupling flange connection (DE 35 03 148 C2) the tensioning device is formed by single, split annular spring elements, whose opposite ends, assigned to their severing point, rest against the opposite sides of the flanges to be connected together and brace them axially relative to each other. In the case of this solution the choice of such annular spring elements and their distribution along the flange periphery allow for significant flexibility with respect to the size and the distribution of the tensioning forces along the periphery of the flange connection. Yet with such a design the assembly time is significant, especially since there is the option of installing annular springs of different tensioning force, and the distribution of the annular springs over the periphery can vary. In addition, such a solution also assumes suitable accessibility and adequate space for the relatively voluminous annular springs.
Furthermore, there exist flange connections (DE-OS 26 14 477; DE 43 17 256 C2), where the flanges to be connected form in their assembly position an annular collar, whose cross section is trapezoidal and which tapers off toward the outside. Said annular collar is held together by axially stressed tensioning elements or a pipe clamp, which is to be braced in the circumferential direction and exhibits suitably inclined flanks.
The object of the invention is to provide a vibration-decoupling flange connection of the class described in the introductory part. Under good assembly conditions, its tensioning device is characterized by low material consumption and simple manufacturability. If desired, it can also facilitate for single tensioning areas an individual determination of the tensioning force.
This object is achieved by an arrangement according to which the tensioning device exhibits, as a multipart constructed tensioning clamp, two separate clamp legs, which stress the opposite flange sides and can be fixed into position through locking in the joined together state. The use of separate clamp legs enables during production greater freedom at lower cost and also increases the assembly options, in that the locking means can also be achieved by means of a combined plug and lock connection. To this end, once the plug connection between the two clamp legs has been produced by swivelling the same relative to each other, the position can be fixed by locking. The clamp legs can be assigned appropriate plug tongues, which engage with the receiving openings of the cover plates. Furthermore, cover plates can be provided with suitable latches that engage with the counter piece. The invention also enables a locking in that the clamp legs are rotated alternatingly relative to each other.
As a multipart constructed tensioning clamp, the embodiment also affords expanded possibilities of distributing the tensioning forces, as desired, over the supports, and in particular by adapting the cross sections of the support-bearing areas of the clamp legs, in particular in assignment to the position of the locking connection.
Especially advantageous is a design of a clamp leg that is configured in the shape of a clamp curve and has three supports, of which two are assigned to the end regions of the arms, and one, to the crown area. For the support located in the crown area, the assignment to a support web is expedient. As a part of the web, which forms the crown area of a clamp leg and connects the clamp arms, said support web is cut free parallel to the web relative to said web. Said free cut up to and into the area of the attachments of the arms can be advantageous.
Other details and features of the invention will become apparent from the claims. Furthermore, the invention is explained below with other features with reference to the embodiments.